1. Field of the Invention
The present invention relates to a method and apparatus for measuring the distance between the equipments on a LAN and detecting the positional relationship between the equipments and, more particularly, to a method and an apparatus for measuring the distance between the equipments on a LAN and detecting the positional relationship between the equipments by collecting and analyzing, by one equipment on the LAN, the information on the other equipments connected thereto on the same LAN.
With the recent demand for common use of resources such as a file and a printer, and the recent demand utilization of data communication, a LAN has increasingly come into wide use. A conventional LAN copes with an increase in the number of ports by utilizing a star type network realized by connecting a hub to a trunk line of a cascade connection of a hub. In addition, a plurality of LANs are connected with each other or a hierarchical network is constructed by utilizing an intermediate apparatus for LAN--LAN connection such as a bridge, a router and a brouter.
As a LAN wiring topology, there are (a) a bus type network, (b) a star type network, and (c) a ring type network as shown in FIG. 16. The bus type network is often seen in a LAN using a coaxial cable ACL. In the star type network, equipments are connected in the shape of a star with an equipment CH called a concentrator or a hub as a center. In the ring type network, adjacent stations STs are directly connected with each other, thereby forming a ring.
With a rapid increase in the scale and the zone of a LAN, much importance has been attached to network management. A protocol for network management such as an SNMP (Simple Network Management Protocol) and a CMIP (Common Management Information Protocol) is standardized and many networks are managed by using these protocols. The SNMP is a protocol exclusively for concentrated management of the equipments constituting a LAN. The SNMP conducts managements such as (1) statistics management of traffic (number of Ethernet packets, number of errors, number of collisions, etc.), (2) management of record data (data value showing the state of the network during a specific time), (3) alarm management (4) host top N management (data for ranking hosts on the basis of values of a statistic item. This is used, for example, to examine N nodes which have transmitted the largest number of data on a specific day.)
In this way, a network management protocol is standardized, but a method of seizing the distance between the equipments on a LAN or a method of detecting the positional relationship thereof has not been established yet. Therefore, a network supervisor cannot grasp the actual layout of the network from a conventional network management application. For example, even when equipments A, B, C and D and a management terminal MU are connected to a LAN in the positional relationship and at the distances shown in FIG. 17A, the network structure is displayed on a screen as shown in FIG. 17B. That is, it is impossible to draw the network structure corresponding to the actual layout on a display screen.
In addition, in a conventional LAN network system, since it is impossible to seize the distance between the equipments, even when the distance between equipments exceeds a preset value, the management terminal is not informed of the fact, or it is impossible to take a measure to prevent a trouble such as a signal attenuation caused by the prolonged distance.
It is also impossible to detect a trouble such as a cable missing and a trouble in an equipment of the LAN in its early stages.